GB2264750A - Preventing unauthorised use of a vehicle fuel pump. - Google Patents

Abstract

The pump 46, preferably mounted within a vehicle fuel tank, has a housing in which there is enclosed an electrical relay 44 closed upon receipt of a preset digital encoded electrical signal. the relay serving to isolate the fuel pump from its power supply. The digital signal may be produced by an optical key (10, Fig. 1) which is inserted into a reader (Figs. 2 and 3) which has two detectors (22, 24), one detecting a clock pattern (14) and the other a data pattern (16) on the key. <IMAGE>

Description

Title Anti-Theft Device for a Motor Vehicle Field of the invention The present invention relates to an anti-theft device for immobilising a motor vehicle.

Background of the invention Much attention has been directed recently to the problems caused by the theft of vehicles. It is obligatory to fit a vehicle with a steering lock but this has not proved sufficient to prevent vehicle thefts. Devices have therefore been proposed which immobilise a vehicle until the authorised user performs an act which enables the engine to be started.

For example, the authorised user may have a further key which generates an electrical signal or he may be called upon to enter a number into a numerical keypad.

It is however very difficult to immobilise a vehicle in such a manner that the anti-theft device cannot in some way be bypassed by a skilled and determined criminal. One approach currently adopted to avoid this problem is to rely on system complexity and perform several connections and disconnections which prevent the engine from being started. Thus, some anti-theft devices have a bulky harness of their own with unmarked wires leading off in all directions and connected at various remote locations into the vehicle wiring harness to open circuit some lines requiring a power supply and short circuiting to live or to earth other lines.

Because a thief does not know the function served by each wire, he cannot quickly short circuit or cut any wires to make the engine start.

This approach is however undesirable as it complicates installation and requires numerous junctions in the wiring harness any one of which will prevent vehicle operation in the event of a malfunction.

Object of the invention The present invention therefore seeks to provide an antitheft device which is easy to install but which nevertheless is highly effective in immobilising the vehicle.

Summary of the invention According to the present invention, there is provided a fuel pump having a housing in which there is enclosed an electrical relay and means for closing the electrical relay upon receipt of a preset encoded digital signal, the relay when open being operative to isolate the fuel pump from its power supply.

The electrical relay of the fuel pump is housed within the pump housing which in turn in some vehicles is fitted to the fuel tank and is totally inaccessible to a would be thief.

The input lead to the relay is from any suitable device which provides an encoded digital signal. Any tampering with this connection lead is unlikely to simulate the same digital pulse train. As the disconnection of the fuel pump from its power supply is carried out inside the pump hous ing, the only way to power the pump while bypassing the open circuit relay would require dismantling of the fuel pump. In certain vehicles, this involves not only removal of the fuel pump but dropping of the fuel tank and dismantling of the exhaust system making it extremely difficult to drive the vehicle away.

Conveniently, the device for sending a digital encoded signal to the fuel pump comprises a key having optically detectable code markings and a code reading device having two electro-optical detectors for sensing the code markings on the key, wherein the digital code of the key read by the reading device is represented by the states of the markings aligned with one of the detectors at positions in which edges of other code markings are aligned with the other detector.

Such a key and reading device are described and claimed in copending Patent Application No.Sdo94/33, filed on the same day as the present application.

Preferably, the key should be a flat elongate key with a regular pattern along one side providing clock signals and a randomly selected pattern on the other side representing the digital code to be produced by the card reading device.

The patterns on the key need to be optically discernible and may comprise opaque regions, reflective regions, regions of different colour or regions of different light polarisation.

It is not essential that the patterns should be visible to the naked eye, in particular since the term light is used herein in a broad sense to include frequencies outside the visible spectrum, namely infra-red and ultra-violet.

The electro-optical detectors may comprise optical couplers consisting of a light emitting diode and a light sensitive transistor. As light emitting diodes require a fairly high current, it is preferred to include in the reading device means for mechanically sensing the introduction of a key and only energising the diodes while a key is being inserted.

The latter means may suitably comprise a micro-switch in the reading device sensing the edge of the key. It is convenient also to discontinue energising the diodes upon detection of full insertion of the key into the reading device and this may be achieved by forming a notch in the key to allow the micro-switch to open again. Such construction is desirable as it provides a feel to the key and the tactile feedback confirms to the driver that the key has been fully inserted.

The circuit to which the output signals of the detectors are supplied can be designed to produce the same digital code regardless of the orientation of the key within the reading device. As a result, no special precaution need be taken to form a key which can only be inserted into the reading device in one orientation.

Preferably, the clock signal pattern is physically longer than the encoded pattern so that it may be sensed first. In this way, the circuit analysing the signals from the detectors may determine which of the signals from the detectors is the reference clock signal.

The circuit connected to the detectors and analysing the signals to determine the digital code of the inserted key forms part of the fuel pump. In this way, the electrical line which carries the signal for immobilising the vehicle is not be accessible near the reading device and it will not be simple by open circuiting or short circuiting any of the lines to simulate the conditions created by insertion of the correct key.

In use, a driver first inserts the optically encoded key into its reading device, which is also mounted within easy reach of the driver. As soon as the key enters the reading device, it closes the micro-switch which powers its electrooptical detectors and also supplies a signal to a microcontroller in the fuel pump to prepare it to receive a digital code. The data signals from the detectors of the reading device are supplied to the circuitry within the fuel pump and the first detected trailing edge signifies to the relay circuit which of the input lines carries the clock or synchronisation signal. The trailing edges of all the pulses from that same detector will then be used as clock signals to load the data signals on the other detector sequentially into memory locations or into a shift register.The serial input from the reading device is thus entered one bit at a time into the memory or shift register, which will then contain, when the key has been fully inserted into the reading device, a digital code corresponding to the key code. If that code is the same as one previously stored into a memory in the circuit, then the electrical relay is closed and permits power to flow to the fuel pump.

The electrical relay should preferably act as a hold-on relay so that even if the key is removed, the pump will remain operational until the engine is turned off and the live connection to the fuel pump is discontinued. This is desirable because the optical key may need to be mounted in a location where is can be accessed by a passenger and its inadvertent removal should not bring the vehicle to a halt.

It is also preferred that if the key has been removed, the hold-on relay should not only remain closed until power to the fuel pump is discontinued but for a short time delay thereafter. This is to ensure that the vehicle will restart if the engine should stall and the ignition key is turned off temporarily while trying to restart the engine.

During withdrawal of the optical key from the reading device, if the leading edges of the clock signal are used to clock the signals from the other detector into memory, the reverse of the stored code is sent by the reading device to the relay circuit. The relay circuit therefore knows not only when a key is inserted but also when it is withdrawn.

This can be used to advantage to prevent attempts to send codes at random to the fuel pump because consecutively received codes which are not the reverse of one another will be recognisable as not having been generated by a key. If desired, the fuel pump relay may remain in its closed posi tion for as long as the optical key is not removed from its reading device, returning to its open state only after removal of the optical key and turning off of the ignition.

It is convenient to use an electronically programmable read only memory to store the reference digital code in the memory within the fuel pump. This enables any key to be supplied initially with any pump unit. When an optical key is used for the first time, its number (preferably after verification) is stored in the non-volatile memory and thereafter only that key can be used for that pump circuit.

In the event of a fuelling problem, it is necessary to be able to test if the anti-theft device is the cause of the fault. To this end, it is possible to provide service keys with dedicated codes to permit certain diagnostic functions to be performed. For example, it is possible to design the micro-controller so that upon receipt of a predetermined code common to all fuel pumps, the fuel pump motor will be energised for a short length of time to allow proper operation of the fuel pump to be tested.

Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of an optical key, Figures 2 is schematic sectional plan view of a reading device, Figure 3 is a front view of the reading device, and Figure 4 is a schematic representation of a fuel pump in accordance with the invention.

Description of the preferred embodiment Figure 1 shows a key 10 with a fob 11, a stem 12 and notches 13 at the end of the stem 12 nearer the fob 11. The key is made of two layers of plastics material transparent to infra-red radiation having embedded between them an optical mask which is opaque to infra-red radiation. The mask comprises two sets of lines 14 and 16 extending in opposite directions from the longitudinal centre line 18. The lines 14 to the left of the centre line 18 as viewed comprise a regular array of lines which may be considered as the clock pattern. The lines 16 to the right of the centre line 18, on the other hand, have varying widths and separation and constitute the data pattern.

The digital number represented by the key is determined by the state of the data pattern (transparent or opaque) at positions coinciding with the trailing edges of the lines of the clock pattern (lines 14). It will also be noted that the clock pattern starts nearer the end of the key than the data pattern thereby permitting it to be identified by the reading device.

The reading device comprises a slot 20 for receiving the stem 12 of the key 10. Two slotted infra-red detectors 22 and 24 (optical couplers each comprising an infra-red diode and light sensitive transistor) are arranged one on each side of the slot 20 to straddle the edges of the stem 12 of the key 10. As the key is inserted into the detectors 22, 24, the output signals of the latter will change between two states depending on whether the portion of the key 10 located in the detector is transparent or opaque.

The reading device further comprises a mechanical microswitch 26 which physically senses the presence of the key within the reading device. When the key 10 is present, the micro-switch 26 produces a signal which turns on the infra red diodes of the detectors 22 and 24 and also transmits a signal to the micro-controller 40 in Figure 4 which analyses the electrical output signals from the detectors. The purpose of the notches 13 at the base of the stem 12 of the key 10 is to allow the micro-switch 26 to close upon full insertion of the key. This prevents further energising of the diodes and can be used by the micro-controller 40 to indicate that the last bit of the serial digital code has been transmitted.

The circuit shown in Figure 4 is completely contained within a fuel pump unit which is itself preferably mounted within the vehicle fuel tank. The circuit has three inputs, the two labelled DATA 1 and DATA 2 being connected to the detectors 22, 24 of the reading device and the third being connected to the micro-switch 26 of the reading device.

The circuit comprises the micro-controller 40 which receives these three inputs and an electronic relay 44 operated by the micro-controller 40 and arranged in series with the live power supply to the electric motor of the fuel pump 46. The micro-controller 40 also performs other functions which are not relevant to the present invention and which therefore will not be described. The micro-controller 40 incorporates a processor and a memory unit which includes an electrically programmable read only memory. The operation of the microcontroller is determined by a programme which is also stored in memory and the method of operation of which will now be described.

The micro-controller 40, when first fitted to a fuel pump, does not have stored in it the digital code of any specific key. Instead the memory locations in which the reference digital code is stored will contain a code indicating that no digital code has yet been stored. The first time a key is inserted into the reading device, the code of that key after suitable verification will be stored in the appropriate location and thereafter the fuel pump will only be usable when that key is inserted in to the reading device.

When a key is inserted, the enable signal produced by the micro-switch 26 will initiate a code reading operation by the micro-controller 40 which will then monitor both of the data inputs DATA 1 and DATA 2 not yet knowing which of these is the clock-signal and which is the data pattern signal.

The first of the two inputs to change state is taken to designate the clock signal and the trailing edge of the each of its pulses will then be used by the micro-controller to clock the data signal of the other input sequentially into random access memory. After a certain number of bits or after the enable signal goes low to indicated full key insertion, the digital code stored in random access memory (or in a shift register) is compared with that stored in the non-volatile memory (ROM) in the manner previously described and in response to a correct match, indicating that the correct key has been inserted into the key-reading device, the electronic relay 44 will be closed to permit power to be supplied to the fuel pump motor.

Until a further enable signal is received by the controller indicating that the key is being withdrawn, the controller will assume that the correct key is located in the reading device and will maintain the electronic relay 44 closed, even if the ignition system should be turned off.

The micro-controller 40 also receives power from the switched power supply line to the pump through a regulator 42. Within the micro-controller, a timing function or circuit ensures that the electronic relay 44 remains closed for a short time after ignition has been switched off regardless of the presence or absence of the correct optical key. This feature is to ensure that in the event of the vehicle stalling it can be quickly restarted even if the encoded key has been removed from its reading device.

While the key is being removed the micro-controller will receive the same digital code in reverse, which corresponds this time to the digital state of the data pattern at the leading rather than the trailing edges of the clock pattern lines in the mask. This code pattern can also be recognised if desired and used to confirm withdrawal of the correct key from the reading device. As earlier mentioned, this pattern reversal can also provide additional security against random code generator based theft devices.

Because a micro-controller is used to operate the electronic relay it is further possible and desirable to build diagnostic capabilities into the programme. It is thus desirable for the micro-controller to recognise predetermined digital codes used in keys available to service engineers and which can trigger certain test routines within the programme. For example, if it is desired to test if the pump is working correctly a key may cause the electronic relay 44 to close for a predetermined length of time sufficient to allow the operation of the pump to be tested. Other keys may be provided to test other functions that might interfere with the vehicle starting. It will be noted in this context that two lines connect the micro-controller 40 to the electronic relay.The second of these lines is for monitoring the state of the relay 44 enabling the micro-controller 40 to confirm if power is available at the output of the relay 44 after an instruction has been sent on the first line to close the relay. The status of the electronic relay 44 can in this way also be verified during fault diagnosis.

The micro-controller 40 may be programmed to open the electronic relay 44 for a long time, say thirty minutes, in response in any attempt to insert a wrongly coded key into the reading device. However, in this case, there is a risk that improper reading of a correctly coded key, for example on account of dirt on the key, may cause the micro-controller to cut out the fuel pump.

To avoid this difficulty, it is preferable to include an error or redundancy code into the digital number represented by the key so that no two possible numbers differ from one another by only one digit. As dirt is only likely to affect one digit, it is possible in this way to distinguish between an incorrectly read key and insertion of an incorrect key.

Indeed, it is possible by the same technique to accept a code which differs from the expected code by only one digit, in the knowledge that the difference could only have resulted from a reading error.

The advantage of incorporating an anti-theft device into the fuel pump is that the entire unit is wholly inaccessible and there is no facility for tampering with the input leads to the unit to simulate the use of the correct key in the reading device.

Claims (17)

1. A fuel pump having a housing in which there is enclosed an electrical relay and means for closing the electrical relay upon receipt of a preset encoded digital signal, the relay when open being operative to isolate the fuel pump from its power supply.

2. An anti-theft system comprising a fuel pump as claimed in claim 1 and a device for sending digital signals to the pump, the latter device comprising a key having optically detectable code markings and a code reading device having two electro-optical detectors for sensing the code markings on the key, wherein the digital code of the key read by the reading device is represented by the states of the markings aligned with one of the detectors at positions in which edges of other code markings are aligned with the other detector.

3. An anti-theft system as claimed in claim 2, wherein the patterns on the key comprise opaque regions, reflective regions, regions of different colour or regions of different light polarisation.

4. An anti-theft system as claimed in claim 2 or 3, wherein the electro-optical detectors comprise optical couplers each consisting of a light emitting diode and a light sensitive transistor.

5. An anti-theft system as claimed in claim 4, wherein the electro-optical detectors operate in the infra-red range.

6. An anti-theft system as claimed in any of claims 2 to 5, wherein the reading device further includes means for mechanically sensing the introduction of a key into the reading device.

7. An anti-theft system as claimed in claim 6 when appended to claim 4 or 5, wherein the mechanical sensing means is connected to permit the diodes of the detectors to be energised only while a key is being inserted into the reading device or withdrawn from the reading device.

8. An anti-theft system as claimed in claim 6 or 7, wherein the mechanical sensing means is a micro-switch actuated by the edge of the key.

9. An anti-theft system as claimed in claim 8, wherein the stem of the key comprises a notch to allow the micro-switch to open when the key if fully inserted into the reading device.

10. An anti-theft system as claimed in any of claims 2 to 9, wherein the code patterns of which the edges are to be detected in the reading device by one of the detectors extend nearer to the end of the key than the other code markings sensed by the other detector.

11. An anti-theft system as claimed in any of claims 2 to 10, wherein the relay within the fuel pump housing is an electronic relay and the means for closing the relay is a micro-controller connected to receive the output signals of the key reading device.

12. An anti-theft system as claimed in claim 11, wherein the micro-controller incorporates a time delay function and is operative to maintain the relay closed for a predetermined time following disconnection of the power supply to the fuel pump.

13. An anti-theft system as claimed in claim 12, wherein the micro-controller has a random access memory for storage of signals derived from the reading device and a read only memory having stored therein the code of the encoded key.

14. An ant-theft device as claimed in claim 13, wherein the read only memory is electronically programmable and the micro-controller is operative to write into the memory the code of the first key introduced into the associated reading device.

15. An anti-theft system as claimed in any of claims 11 to 14, wherein the micro-controller is programmed to initiate diagnostic routines upon receipt of predetermined digital codes from the reading device, generated by the insertion of service keys into the reading device.

16. An anti-theft system as claimed in any of claims 11 to 15, wherein the micro-controller is operative to maintain the relay in a closed condition for as long as the correctly encoded key remains in the reading device.

17. An anti-theft system constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.